Digital Receiver with Interference Suppression for Microwave Radiometry
چکیده
A new receiver architecture for use in L-band microwave radiometers is proposed. The receiver is based on analog-to-digital conversion of a significant bandwidth of received emissions, and includes sufficient dynamic range so that digital processing can be performed to remove at least 30 dB of radio frequency interference (RFI). The resulting radiometer should be able to operate outside the 1400-1427 MHz frequency band allocated for passive observations, enabling more accurate brightness temperature measurements, use of alternate L-band frequency choices for improved geophysical parameter sensitivities, and/or reduced correlator complexities for interferometric systems. The interference suppression algorithms used, which have been successfully demonstrated with Earth based radio astronomy systems, are based on adaptive filtering and parametric approaches implemented in real time through reconfigurable digital hardware. A microwave radiometer using a 100 MHz bandwidth centered at 1413 MHz will be considered in this project. An instrument design, prototype development, laboratory tests, and ground-based measurements are proposed over the three year project period to demonstrate successful brightness temperature measurements even with significant interferers present. A basic instrument design concept and assessment for space-based operations will also be developed, along with advanced suppression algorithms which adapt to the RFI type encountered. The technology proposed (if successful) can play an important role in achieving ESE research goals related to soil moisture and sea surface salinity sensing, and can be incorporated into current and future plans for space based Lband radiometers. The technology proposed is also relevant to radiometers operating at other frequencies; basic design architectures for lower and higher frequency operations will also be explored. Other advantages of digital receiver architectures including improved calibration and diagnostic procedures, implementation of near-true-time-delay algorithms for interferometric systems, and flexibility for in-flight modification of receiver characteristics will also be evaluated for future systems.